Thioanisole is a useful pharmaceutical intermediate. A known method for production of thioanisole involves methylation of thiophenol with methyl chloride in aqueous base. Hiroshi, I. et al., Japan Kokai Tokkyo Koho 94-95830, April, 1994. However, thiophenol is a costly raw material for thioanisole production.
A variety of other synthetic reactions for certain arylalkylsulfides are known. See for example, Barrett, G. C. "Sulfides" in Comprehensive Organic Chemistry, Edited by Barton and Ollis, Pergamon Press, 1979, and references cited therein. These include: Lewis acid catalyzed alkanethiolation of arenes using dimethyldisulfide or its derivatives, nucleophilic aromatic substitution of aryl halides with alkanethiolate salt, acid catalyzed alkanethiolation of aryl alcohols using alkane thiols, Pd-catalyzed alkanethiolation of arylhalides with alkane thiols, nucleophilic aromatic substitution of alkanethiolate with diazonium salt of arylamines, etc. Many of these alkanethiolation reactions work well with activated arenes such as phenols or anilines, but have not proven suitably effective for alkanethiolation of inactivated benzene itself. Indeed, only a few examples of thioanisole synthesis from benzene are known. For example, in Brintzingher, L., Chem. Ber. 1953, 86, 557, 562, it is shown that methanethiolation of benzene with methanesulfenylchloride in the presence of one equivalent of AlCl.sub.3 produced a yield of about 50%. Xylene and mesitylene were methanethiolated with methanethiosulfonate in the presence of one equivalent of AlCl.sub.3, but not benzene or toluene. See Kloosterziel, H. et al., Chem. Comm., 1971, 1365. It appears that there have been no synthetic reactions reported enabling efficient alkanethiolation of benzene. This invention provides such a process.